<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<script>
  class Parent {
    constructor(height, width) {
      this.height = height;
      this.width = width;
    }
  }

  class Children extends Parent{
    constructor(sideLengh){
      super(sideLengh,sideLengh);
    }

    get area(){
      return this.height*this.width
    }
    set sideLength(newLength){
      this.height =newLength;
      this.width = newLength
    }
  }
  let square = new Children(2);
  console.log(square);
</script>
</body>
</html>